Welcome, @tommy1st! In order to sell and buy on the classifieds here on Head-fi you must have 15 posts (like the one you just made) and 30 days under your belt. The reason is to try to combat trolls and spammers and scammers from getting a hold here on the site. In the mean time, the best thing you can do is to make some posts so you get up to 15 total by the end of a month, then you can male your ads and sell your gear. Sorry, we know it is an inconvenience to have to wait a month. Hope the information helps clarify things.
I think I already made 15+ posts. Can I now post in Selling/Trading forum? I have some gear really want to sell.